Development of a Method for Determining the Residual Life of Structural Elements with Cracks Under the Action of Load and Corrosive Environment, as well as the Application of Corrosion Inhibitors to Enhance It

Abstract

A developed method for determining the lifespan of structural elements with large-scale cracks of complex geometry under the influence of long-term static loads and corrosive environments. The method is based on an appropriate computational model, which relies on the first law of thermodynamics for the elementary act of local failure (crack propagation), some fundamental principles of physical chemistry, as well as the basic principles of fracture mechanics. The advantages of this method over existing ones are substantiated. The application of the method is demonstrated through examples involving the determination of the residual life of such structural elements as torsion and a pipe with small cracks made of 45KhN2MFA steel (tempered at 470 K and 725 K) under the influence of long-term static loading and distilled water. As the cracks are considered small, we have constructed a computational model in terms of deformation parameters, including a well-known counterpart in fracture mechanics, crack opening at the crack tip δt. At the same time, based on available experimental data from the literature, it is substantiated that the application of existing linear fracture mechanics methods in stress intensity factors KI for implementing the mentioned problems, the application of existing linear fracture mechanics methods is inappropriate. To determine the residual life of structural elements using this method, it is necessary to have kinetic diagrams in coordinates of the growth rate of small cracks and the crack opening at the crack tip, which means V ∼ δt. These diagrams are constructed here using the provided formulas for determining δt and diagrams are constructed here using the provided formulas and known experimental data for 45KhN2MFA steel under the influence of distilled water and static tension. Using the mentioned method, the residual lifespans of the torsion and the pipe were calculated under the influence of long-term static loading and distilled water. Additionally, the effectiveness of water solutions of well-known inorganic corrosion inhibitors on the residual lifespan of the mentioned structural elements was verified through calculations. It was found that the residual lifespan effectively characterizes the performance of corrosion inhibitors, which can be applied in engineering practice.